One or more aspects of the present invention relate to a technique for supporting secondary use of content of electronic works.
With the spread of electronic publishing and e-books, cases of publishing official or private electronic works on a network are on the increase.
However, unauthorized use, illegal reproduction, unintended falsification, and the like of electronic works are commonplace.
Accordingly, in many cases, an author unwillingly sacrifices the convenience to protect his/her rights, and publishes an electronic work on a network in a way that prohibits reproduction or editing.
Sacrificing the convenience in the above manner raises a problem that an electronic work becomes hard to use for users (for example, readers and secondary users) of the electronic work.